A PCD compact is formed by sintering individual diamond particles together under high pressure and high temperature (HPHT) conditions. Sintering is commonly done in the presence of a catalyst, such as cobalt, which promotes diamond-to-diamond bonding.
In general, a compact may be characterized generally as an integrally bonded structure formed of a sintered, polycrystalline mass of abrasive particles, such as diamond or CBN. Although such compacts may be self-bonded without the aid of a bonding matrix or second phase, suitable bonding matrixes include metals such as cobalt, iron, nickel, platinum, titanium, chromium, tantalum, or an alloy or mixture thereof. The bonding matrix, which is provided at from about 5% to about 30% by volume, additionally may contain a recrystallization or growth catalyst such as aluminum for CBN or cobalt for diamond.
The basic HPHT method for manufacturing polycrystalline compacts entails placing an unsintered body of abrasive, crystalline particles, such as diamond or CBN, or a mixture thereof, within a cup which is disposed within the reaction cell of a HPHT apparatus. Additionally placed in the enclosure with the abrasive particles may be a metal catalyst if the sintering of diamond particles is contemplated, as well as a pre-formed body of a cemented metal carbide for supporting the abrasive particles and to thereby form a supported compact therewith. Alternatively, catalyst may migrate or be swept into the matrix of abrasive particles before and/or during sintering. The contents of the cell then are subjected to processing conditions selected as sufficient to affect intercrystalline bonding between adjacent grains of the abrasive particles and, optionally, the joining of the sintered particles to the cemented metal carbide substrate or support. Such processing conditions generally involve the imposition for about 3 to about 120 minutes of a temperature of at least about 1200° C. and a pressure of at least about 20 kbar, and typically at pressures above about 40 kbar and at temperatures from about 1200° C. to about 2000° C.
As to the sintering of polycrystalline diamond compacts, the catalyst metal may be provided in a pre-consolidated form disposed adjacent the crystal particles. For example, the metal catalyst may be configured as an annulus into which is received a cylinder of abrasive crystal particles, or as a disc which is disposed above or below the crystalline mass. Alternatively, the metal catalyst, or solvent as it is also known, may be provided in a powdered form and intermixed with the abrasive crystalline particles, or as a cemented metal carbide or carbide molding powder which may be cold pressed in to shape and wherein the cementing agent is provided as a catalyst or solvent for diamond recrystallization or growth. Typically, the metal catalyst or solvent is selected from cobalt, iron, or nickel, or an alloy or mixture thereof, but other metals such as ruthenium, rhodium, palladium, chromium, manganese, tantalum, and alloys and mixtures thereof also may be employed.